How To Make/attach Goldfish Tail And Fins For Cake Topper?

I'm making an 8" round cake with a goldfish topper for next weekend. (For whatever reason, the pic would not attach and this question would not post to the forum when I included a link.) I'm making the fish body out of Rice Krispy Treats covered in fondant. I'm struggling a bit on the best way to do the tail and the top fins. I'm thinking that straight fondant or gumpaste would not be the way to go, since it would be heavy. I'm leaning toward cutting these shapes out of foam core and then covering them with fondant. Does that seem right? Also, I thinking that I would attach the tail and fins to the RKT body with either toothpicks or thin skewers. Does that seem right? I'd really appreciate any ideas or feedback. Thanks so much for your help!

I like what Diane had to say. That's how I would do it. If you use the gum paste, or fondant gumpaste mixture, and let it dry (with tooth picks in it) I think you would be good to go. That being said, I am not too sure of the size of the fins/tail you are speaking of. If they are larger then 3-4 inches, then perhaps you do want to wrap the foam like you were talking about above. IF they are just 3-4 inches tall to begin with, then I think you should be okay without the foam.